#!
sub foo
{
    $age  = 20;        # the default parameters
    $name = "Andy";
    my %p = @_;
    $age = $p{'Age'} if(exists $p{Age});
    $name = $p{Name} if(exists $p{Name});
    print "Name: $name\nAge: $age\n";
}

foo;
foo( Name=>Henry);
foo( Age=>30,Name=>Mary);    
foo( Name=>Mary,Age=>30);  
